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VWF Factor - Von Willebrand Factor - Von Willebrand Factor Activity - Factor VIII: VWF - Ristocetin Co-factor - RAF - R:CoF


Patients with blood type O have approximately 25% lower VWF values than those with other ABO blood types. Many experts agree that a VWF cutoff of 30% supports definitive diagnosis of von Willebrand Disease (VWD). Referral of such patients to a Hematologist with hemostasis experience is recommended. Further testing may include repeat testing, VWF Multimer Analysis, Ristocetin-Induced Platelet Aggregation (RIPA), VWF Collagen-Binding Activity, or Platelet-binding Studies. Additionally, as there are many patient and sample factors that can influence VWF results, patient values in the 30-50% range may warrant repeat testing, particularly if there is strong family and bleeding history.

Specimen Collection Requirements


Whole Blood light blue top tube (3.2% Buffered Sodium Citrate)


For detailed specimen collection and handling, see Coagulation Specimen Collection Guidelines.

If the patient is on medication, list the medications on the lab requisition. Patient should not have received blood products in the previous 2 weeks. Due to short stability, whole blood specimen tubes must reach the testing department within 4 hours, otherwise submit frozen plasma aliquots. If submitting whole blood, transport at ambient temperature (15-25°C) in original unopened tube. If submitting frozen plasma aliquots, specimens must remain frozen (-20°C) during transport.

STAT Requests: Available 7 days/week. Must notify Special Coagulation Department (503 413-5120) to make arrangements. Specimen must be received by 2 pm at Legacy Central Lab.

Preferred Volume

Two 2.7 mL whole blood or two 1.0 mL frozen plasma aliquots

Minimum Volume

One 2.7 mL whole blood or one 1.0 mL frozen plasma aliquot


Whole Blood: Ambient (15-25°C)

Plasma: Frozen (-20°C), aliquots must remain frozen during storage and transport

Rejection Criteria

Whole Blood or Plasma, Refrigerated (2-8°C)

Clotted samples, samples collected in containers other than 3.2% Buffered Sodium Citrate, tubes filled less than 90%, samples from patients with a Hematocrit greater than 55%, hemolyzed samples due to ex-vivo causes (i.e., difficult draw, poor sample draw), whole blood samples that were frozen before processing


WHOLE BLOOD: Ambient: 4 hours

PLASMA: Ambient: 4 hours; Frozen: (-20°C) 2 weeks, (-70°C) 6 months

Testing Information


Daily, Mon-Friday


1-3 days


Latex Immunoassay

Reference Values

Reference Values

Varies, see report.

CPT Codes


Last Updated: Thursday, January 5, 2017 03:41:06 AM

Client Services: 503-413-1234